High frequency amplifier circuit



I March 30, 1943- y A. VAN DER ZIEL Erm. 72,314,958, A HIGH FREQUENCIAMPLIFIER CIRCUIT Y FII-ed Jan. 18, 1941 I I F/g/ v 17 l A 'I' f* n Vv\ y vvv" "I 72 CLL \`3| f I z I i 7- *Y 2 .--IC l L1 z C'2 3 l 'LW VMACHO/af I H F, 3 'CHO/(E c I 2 TI T/Q 9 fw |l .Y n

2520 *y z; "i"

ATIORNEY- I Patented Mar. 30, I

;V AUNITED sTATas PATENT; g1 s A A' nlonmaousnlgwnmwh I' Aldert van der Ziel and Kornelis SwierKnol,

, the input damping is approximately zero or negal Eindhoven, Netherlands;

Property Custodian Ivested in the Alien I Application January 18, liliLsel-lalm),v gig-4,96 l y IntlieNetherlandsMarchzl, 1940y y l comme. (ci. 1795-171) f In the cepending appneeuon, ser. No. asaoas,

- med Mey 3, 1940. there is described e. high-fre-. quency amplier circuit comprising at least one amplier valve whose cathode is provided with K in. which capacities are connected between the.

control grid and the point of thev cathode which is connected to the cathode lead included in the input circuit and between thecontrol grid and that end of the cathode lead included in the out- -put circuit which is not connected to the cathode, and one or both cathode leads comprises or comprise 'impedances of which at least one has an inductive'character,. said capacities and impedances being proportionedin such manner that tive. 1 p

v"iAn amplier valve having ja directly heated cathode naturally'comprises already two cath- @de leads, namely, the two heating current leads. 12ms, in principle. use may be made o1' the circ it shown in Fig. l ofthe accompanyingdrawing which is set out in greater 'detail hereinafter andlin which the two heating-current supply con'- ductorsperform the functions of the above-mentioned cathode leads. l

This circuit, however, has the disadvantage that the resistance ofthe filament brings about a supplementary damping of the input oscillatory circuit. Y

According tothe invention this disadvantage is obviated by providing a cathode with at leastk threeleads, two of which are connected to one ci the ends V*of the `cathode and'are included, for, the oscillations to be ampliiied, in the input circuit and in the output circuit respectively, Whereas a third lead is connected to the other end of the cathode and onlyserves for. the supply of heating current. j. In order that. the invention may be clearly understood and readily carried into effect it will now be described more fully with reference to the accompanyingA drawing, in which y Fig. l shows the circuit above referred to ac-` cording to the prior application with'the use of a directly heated tube, and l j Figs.l 2 and 3 show` embodiments according to the present invention."

The circuit shown in Fig. 1 includes an ampli- .input oscillatory circuit" i2 which is connected on theonehand to the coniied are fed to an trol grid 3 andA ou the other handgyia one ci' the cathode leads. to, thefca'thode 2. The anode 'I is connected to the cathode '2 'v ia .aoutputoscillatory circuit I8. `from which the amplified ofi, and via the othergcathoscillations are. taken ode lead.

The cathode leads include inductances Li andv 'l Le and the point 8 of the inductace L1 which "i 'pointis adjacent to the cathodais connected to the'control grid 3 viaa capacityA Ci and thefend or the inductance L: ('91 which' is remote from the cathode is connected to the control grid vla a capacity Cz.

`The screening grid l yis connected, via a ca-` pacity Cs, to that end of the inductancev Lelwhich is remote from the cathode so that theatural The heatingcurrent which-is ureceii'led from a 'battery l1 .is supplied tothe cathode 2 via highfrequency choke coils Iiandl ,which prevent any short-circuit of the inductances Lik and vL:

fier valve comprising a directly heated cathode 2, provided with two leads, a control grid 3, a 'screening grid 4, a suppressor grid 5 and an anode 1. The high-frequency oscillations to be amplifor the oscillations tobe amplified. lThe other sources of supplyy are omitted for thesake of simplicity.

As set out-'in thev` prior applicationit canbeff l y ensured by correct proportioning of the elements L1, L2; C1 and C2' that the input damping which oecursjou'e te the nuire' transit time ef the elec-1` v trons is suppressed" so that the consequential-inputv damping becomes zero or.' even negative. The elements Li, La,'C1 and C2 can be'iormedin part but not all of themby the natural inductances of the cathodeleads andthe natural tube'capacie' ties.

^ However, 'the circuit has the disadvantage that the resistance of the filament is connectedy in parallel with the input-oscillatory circuit I2 via the capacity C2 andthe inductances L11-'and Le V so that an undesired'supplementaryv dampinglof the input oscillatorycircult is brought about.

` According'to the invention this clisadvantage may be obviated by the use of a directly heated tube comprising three cathode leads as shown in Figs`.2and3. n V l.

In the circuit shown in Fig. 2 the left-hand lend of the fuement z has connectedy teit two leads which are included rrespectively in vthe input circuit and in they -output circuit and in which inductances s L1 and La -are included. s Thev right-hand end ofthefilarnent has connected toit a third lead -which solely vserves for the supply ot heating current and in which a highfrequency choke coil IB is included. The lead included inthe output circuit is used as a returnlead for the heating current and for this purpose the heating current supply battery'is connected between the `end of the choke'coil Il which is.

remote from the cathode andthe point S. Asa rule, the heatingv current supply battery must be earthed so that in this case the output oscil-` latory circuitis also connected to earth in a highfrequency manner.

the output oscillatory circuitl'and the end of the choke coil i8 which is remote from the cathode are jointly connected to earth,V whilst the battery is short-circuited by a condenser Il in a hithfrequency manner. Instead thereof the point l could, of course, be connected to earth.

The choke coil Il must be possessed of a considerable impedance for the oscillations to be amplified sincev the resistance of the ,filament 2 which is connected in parallel with the input osclllatory circuit via the capacity Cn," the con-y denser IO, the choke coil 1I8` and the inductance In' may otherwise exercise a vdamping on that circuit.

In the circuit arrangement shown in Figi; the

those ends of the choke coil vI Il and the inductance Li'which are remote from the cathode.

If the put grid and an anode, two leads connected to one cathode terminal and a third lead connected In this case the circuitv arrangement may be as shownyin Fig. 2 in which to the other cathode terminal, input and output circuits connected respectively to the input grid and to the anode, the grid return oi' the input circuit being connected to one of the firm -two cathode leads, the plate return of the output spect to high frequencies.

` 2'. A circuit according to the invention defined in claim 1 wherein the grounded terminal of the heating source is connected to the third lead.

battery is lto be connected to earth the input oscillatory circuit is thus also connected to earth. The earth connection concerned may be provided, for example, as shown ln the figure, at the end of they inductanceLrwhich is remote from the cathode.

"The circuit shown in Fig. 3 oiiers the advantage that the choke coil I8 may generally be pos-f Y sessed of a lower impedancethan in the circuit shown in .Iig.'2. On the other hand theconnectlon of the input oscillatory'circult to 4,earth entails some difficulty due to the capacity genery 'ally present betweenthat end of the output oscillatory Acircuit vI0 which'fis j connected to the in addition .brings about a supplementary damp' ing of the input oscillatory circuit. Ii the input oscillatorycircuit is earthed the anodelead and the 'output oscillatory circuit have therefore pref-V erably to be screened capacltatively relatively to earth so that the capacity 20 is removed, it being necessary for the screening to be connectedto po'intl. v .v

II the output oscillatory circuit is connected to earth, as is effected in the circuit 4arrangement shown in Fig. 2, 'acapacitative screening of the said kind is redundant.

' What we claim is:

11A circuit for the amplification of'high frequencies, comprising an electron discharge tube provided with at least a directly heated filamentary cathode having two terminals, a signal in- 3. A circuit according to the invention defined in claim l wherein the groundedterminal of the heating source is connected to the cathode lead to which the input circuit grid return 'is connected. F' j,

4.V A circuit according to the invention deiined in claim. I `wherein an inductance is connected to each of the twoiirst mentioned cathode leads, said inductances being included respectively in the input and output circuits, and a high i'requency choke coil connected to the third cath-` delead. 5. Avcircuit for the amplification of high frequencies, comprising A'an electron discharge tube provided with at leastl a directly heated filamentary cathode, a signal input grid, a screen grid and an'punode, the cathode having two terminals with a pair of leads connected to one and a third lead connected to the other of said terminals, an impedance connected to each of said pair of cathode leads,`input and output circuits connec ed'respectively to the input grid and to the anod '(1 the'grid return of the input circuit being con@A nected to the low potential end of the impedan connected to one of the pair of cathode leads, t plate return of the output circuit being connected to the low potential end oi' the impedance `connected to the other of the pair of cathodeleads, a condenser connected between the signal input gridand the cathode` end of the impedance included in the input circuit capacitive means connected between the signal input grid and the low potential end of the cathode impedance included in the output circuit, a high fr equencychoke coil connected to thevthird lead, a lsource of heating current having one terminal grounded connected between said choke coil andhone of the cathode lead impedances,v and means for short-circuiting said heating current source with respect' tofhig'h frequencies.

6'. Ajcircuit according to the invention defined in claim 5 Awherein .the grounded terminal of the heating source is connected to the end ofthe high frequency choke coil remote from ,the cathode 

